Obstacle detection method and system, particularly for systems for assisting the parking of vehicles

ABSTRACT

An obstacle detection system, particularly for assisting car parking that comprises a control unit and a plurality of sensors, which comprise emitters-receivers for emitting an ultrasonic signal and for receiving an echo signal reflected by at least one obstacle and an evaluator for the parametric evaluation of the received echo signals, the evaluator comprising a polling module suitable to determine, for each sensing, the number of times for which the received signals are repeated and to reject the signals that are repeated for a number of times that is lower than a preset number.

The present invention relates to an obstacle detection method andsystem, particularly for systems designed to facilitate the parking ofmotor vehicles.

BACKGROUND OF THE INVENTION

During maneuvers for parking a vehicle, it is not possible to perceiveexactly the distance between the vehicle and the obstacles that lie inthe parking area, particularly during reversing maneuvers or maneuversfor approach on the opposite side with respect to the driver. Moreover,it is not infrequent to find oneself in a condition in which someobstacles are completely concealed and invisible to the driver, asoccurs in the case of obstacles located in corners that are covered bythe vehicle structure or are very low, for example the typical bollardsused to delimit parking areas, or simple poles.

In order to solve the drawback and thus avoid unpleasant accidents,systems are known which are provided with sensors for detecting thedistance between the motor vehicle and the surrounding obstacles.

Systems using ultrasonic sensors are mainly used for measuring thedistance between an obstacle and a motor vehicle; these sensors detect asignal emitted previously by a radiating element located in the vicinityof the sensor and reflected by an obstacle that lies proximate to thevehicle.

During an adequate time window, the received return signal, known asecho signal, is compared with a threshold value, and if said thresholdvalue is exceeded, the sensor generates a warning signal.

In these systems, it is particularly important to avoid the emission ofincorrect warning signals and to increase the precision of the assistedparking system. Incorrect warning signals refer in particular to signalsreflected by objects that do not constitute a danger of collision withthe vehicle, such as for example the ground, the optional towing hookmounted on the vehicle, particularly distant obstacles, or signalscaused by noise.

For this purpose, currently it is known to adjust the time window so asto exclude from the comparison with the threshold values the signalscaused by particularly distant obstacles. The duration of the timewindow in fact determines the monitoring depth of the system.

As an alternative, it is common to vary the duration of the signalsemitted by the radiating element of the sensor or to vary the powerradiated by said signals.

Finally, it is also known to act on the threshold values, which can varyaccording to time. Generally, the threshold values are reducedmonotonically over time until the end of the time window, in order toprevent the system from generating warning signals caused by extremelyproximate signals produced by the reflection of the ultrasound forexample against the ground or against the towing hook.

Other known systems adapt the threshold values to the physicalparameters of the car in order to further increase the precision of thesystem. Moreover, these threshold values are changed dynamically alsoaccording to the direction of travel of the vehicle, so as to increasethe sensitivity of the sensors located in the direction of travel andreduce the sensitivity of the remaining ones.

The need to detect the various obstacles that are present around thevehicle and to take into account the various factors described above inorder to provide increasingly accurate information is a requirement thatstill stands despite the existing solutions.

In particular, one of the problems that most significantly affect thesensing devices of the background art is reliability, i.e., theassurance that the warning signals are emitted exclusively at anobstacle. For this purpose, it is necessary to avoid the emission ofincorrect warning signals caused by noise, which may confuse the driver,and therefore increase the precision and reliability of the system.

SUMMARY OF THE INVENTION

The aim of the present invention is to eliminate the drawbacks mentionedabove in known types of obstacle detection system, by providing anobstacle detection system that minimizes the emission of incorrectwarning signals and thus increases the precision of said system.

Within this aim, an object of the present invention is to provide anobstacle detection system that is capable of adapting the sensitivity ofthe sensors to physical and environmental parameters and to thearrangement of the obstacles.

Another object of the present invention is to provide an obstacledetection system that is more flexible and optimized.

Another object of the present invention is to provide an obstacledetection system that requires a reduced number of electronic componentsfor its operation.

This aim and these and other objects, which will become better apparentfrom the description that follows, are achieved by an obstacle detectionsystem, which comprises a control unit and a plurality of sensors, saidsensors comprising means for emitting an ultrasonic signal and forreceiving an echo signal reflected by at least one obstacle and meansfor the parametric evaluation of received echo signals, characterized inthat the means for parametric evaluation comprise means suitable todetermine, for each sensing, the number of times for which the receivedsignals are repeated and to reject the signals that are repeated for anumber of times that is lower than a preset number.

Conveniently, the parametric evaluation means further comprise meanssuitable to drive the power radiated by the signal emission means andmeans suitable to compare the signals received by the echo signalreceiving means with threshold values.

The proposed aim and objects are also achieved by an obstacle detectionmethod, which comprises the steps of determining, for each sensor thatbelongs to the activation cycle, the power to be radiated, emitting thecorresponding ultrasonic signals, and receiving the echo signalsreflected by at least one obstacle; determining, on the basis of thereceived echo signals, the distances of the corresponding sensors fromthe obstacle and amplifying the received echo signals according to theircorresponding distances; selecting the threshold values with which theamplified signals according to the determined distances are to becompared; and is characterized in that it comprises the step ofdetermining, for each sensing cycle, the number of times for which thesignals that exceed the respective selected threshold values arerepeated and, if said number is greater than a preset value, generatinga warning signal.

Conveniently, the obstacle detection method further comprises the stepsof: determining the order of priority of the individual sensorsaccording to the calculated distances; determining the activationsequence of the sensors according to the determined order of priority;and adapting the sensor activation cycle according to the determinedactivation sequence.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will becomebetter apparent from the following detailed description of a preferredbut not exclusive embodiment of the obstacle detection system,illustrated by way of non-limiting example in the accompanying drawings,wherein:

FIG. 1 is a schematic view of the architecture of the system accordingto the invention;

FIG. 2 is a more detailed diagram of the sensors of FIG. 1;

FIG. 3 is a block diagram of the sensor used in the system according tothe invention;

FIG. 4 is a schematic view of a scenario in which a sensor detects anobstacle;

FIG. 5 is a block diagram of the management of each individual sensor;

FIG. 6 is a schematic view of a particular scenario in which differentsensors detect different distances from one or more obstacles.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown schematically in FIG. 1, the obstacle detection systemcomprises a control unit 1, which is suitable to manage a variablenumber of sensors 2 connected to the control unit 1 by means of at leastone bus 3 and comprises memory means 10. The control unit 1 mayoptionally be integrated in devices that already exist within the motorvehicle and are connected to the internal network, typically of the CANtype, of the car.

The sensors 2 comprise parametric evaluation means, such as amicrocontroller 4 for driving signal emission means and such signalemission means formed by a transducer 5 capable of emitting andreceiving ultrasound.

For this purpose, the microcontroller 4 comprises power driving means,such as a module 7 for driving the power of the signal radiated by thesignal emission means, such as the transducer 5 by varying the number ofpulses sent to the transducer 5 and the supply voltage. Moreover, thetransducer receives from the microcontroller 4 a signal which determinesthe time window for listening for the echo signal.

In order to emit the ultrasound signal, the supply voltage reaches thetransducer 5 across a transformer 6, which raises in its peak-to-peakvalue according to the driving of the microcontroller 4.

Further, the microcontroller 4 comprises comparison means, such as amodule 8 for comparing the reflected signal with dynamically optimizedthreshold values. The module 8 further amplifies adequately the receivedecho signal before performing the comparison.

Moreover, the microcontroller 4 comprises polling means, such as afilter module 9, which is suitable to eliminate echo signals detected insuccession a number of times that is smaller than a preset threshold.The filter module 9 recognizes false reports, caused for example bynoise, on the basis of the number of repeated sensings; only echosignals that are repeated for a sufficient number of times areinterpreted as signals that indicate obstacles and are then subjected tocomparison by means of the comparison module 8.

The modules 7, 8, 9 are configured in order to optimize the coverage ofthe space that they face and also to avoid detecting echoes generated byfixed obstacles, such as for example the towing hook. For this purpose,the monitored space is divided into reading regions, for which specificvalues of the configuration parameters of the modules 7, 8, 9 aredefined. These parameters take into account several factors, such as forexample environmental factors, the distance of the obstacles from thevehicle and their spatial arrangement, and are optimized dynamicallyaccording to the previously measured values.

The obstacle detection system operates as follows.

When the system is activated (step 100 of FIG. 5), the control unit 1sends selectively an activation pulse to the sensors 2, which start toemit ultrasound signals. During the movement of the vehicle 20 towardany obstacles 30, said obstacles are struck by the waves radiated by thesensors and reflect them, generating an echo, which is received by thesensors 2, as shown schematically in FIG. 4.

In detail, in step 105 the microcontroller 4 determines the power to beradiated on the basis of the preceding sensings, acting on the supplyvoltage in input to the transformer 6. Depending on said supply voltage,the transducer 5 emits ultrasound signals and, in the presence ofobstacles 30, receives their reflected signals, i.e., an echo signal.

If no echo signal is received, the sensing process restarts from step100, in which the control unit 1 sends the activation signal cyclicallyto the sensors 2.

If instead there is an echo signal, in step 115 the microprocessor 4 ofthe sensor 2 that detects it determines the possible distance of theobstacle 30 and amplifies the signal adequately according, among otherfactors, to the determined distance.

Depending on the calculated distance, the microcontroller 4 furtherselects the threshold value with which the amplified signal is to becompared. The amplified signal and the adequate threshold value arecompared in step 120. If the amplitude of the signal does not exceed thethreshold value, the echo signal is ignored (step 125) and the processrestarts from step 100, in which the control unit 1 sends an activationpulse to the sensor 2.

If instead the amplitude of the signal exceeds the threshold value, themicrocontroller 4 compares, in step 130, the received signal with thesignals received in preceding cycles and counts the number of times forwhich said signal is repeated. If said number of repetitions exceeds athreshold value of the number of cycles (step 135), the sensor 2 sendsthe calculated distance to the control unit 1. The control unit 1 thusactivates the signal that warns of the presence of an obstacle 30 andstores in the memory means 10 the value that corresponds to thecalculated distance, associating it with the sensor 2 from which itarrives. The warning signal may optionally vary according to thedistance value sent to the control unit 1.

In a negative case, instead, the echo signal is ignored (step 125) andthe cycle restarts from step 100 for activating the sensors 2.

Depending on the values of the distance of the obstacles 30 from theindividual sensors 2 received by the control unit 1, the control unit 1determines, in step 145, the priority of the individual sensors 2,determining a sequence for polling the sensors 2, and adapts theactivation cycle accordingly.

Polling priority is based on the distance detected after the scanning ofeach sensor 2. The distances stored in the memory means 10 are usedinitially to determine which sensor 2 is detecting the closest obstacle30. The value of the distance that corresponds to the minimum determineddistance receives the addition of a priority threshold value, and thenew value is stored in the place of the detected minimum distance.

The sensor thus determined is then granted the priority status and thesensing cycle is adapted so as to poll the prioritized sensor morefrequently than the non-prioritized sensors.

For example, it is possible to alternate the polling of the prioritizedsensor with a non-prioritized sensor, as shown in FIG. 6.

In the particular example of FIG. 6, the minimum distance x1 is detectedby the sensor S2, which is given priority status. The polling cycleaccording to this particular implementation is therefore S2, S3; S2, S4;S2, S1; S2, S3, and so forth.

If, during successive polling cycles, at least one of the otherdistances decreases to a value that is lower than the sum of the minimumdistance value and the priority threshold value, the correspondingsensor 2 also is given priority status and the obstacle detectionsequence is adapted so as to poll all the prioritized sensors morefrequently than the non-prioritized sensors.

Again with reference to the example of FIG. 6, if the distance x2decreases below the sum of the minimum distance value and the prioritythreshold value, then S3 also obtains priority status.

One polling that is possible in this case may alternate anon-prioritized sensor with the sequence of prioritized sensors,starting from the sensor that corresponds to the minimum detecteddistance. The polling sequence in this case would be S2, S3, S4; S2, S3,S1; S2; S3; S4, and so forth.

In an alternative embodiment, it might also be possible to exclude fromthe polling, for a preset number of cycles, the sensors that initiallyhave detected no signal. In this manner, the number of sensors activatedat each cycle is reduced, thus reducing the time between two successivepollings of the sensors that detect an obstacle.

It has thus been shown that the described method and system achieve theproposed aim and objects. In particular, it has been found that thesystem thus conceived allows to overcome the limitations of thebackground art, since the module for eliminating the echo signalsdetected in succession fewer times than a preset threshold ensures thatwarning signals are not generated in case of noise sensings, allowingthe system to be much more precise in differentiating actual obstaclesfrom incorrect signals.

Further, the combination of the three modules for the parametricevaluation of the detected signals allows the system to be more flexiblein sensings and at the same time more precise.

Moreover, it has been found that the method can be implemented byconnecting all the sensors to a single bus and optionally integratingthe control unit in another device linked to the CAN network provided incars. This system allows to reduce the number of electronic devices thatare present in the car, offering space saving advantages, a consequentreduction of the production costs of said vehicle, and a reduction ofpower consumption in operation.

Further, the fact that parametric evaluation occurs within the sensorsand is not centralized in the control unit allows the system to be muchfaster during the evaluation step.

Clearly, numerous modifications are evident and can be performedpromptly by the person skilled in the art without abandoning the scopeof the protection of the appended claims. For example, it is obvious forthe person skilled in the art that the switch of the sensor can beprovided in any manner, for example by means of any type of transistor.

Likewise, it is evident to the person skilled in the art that the sensorcan operate on one or more parameters, such as the time window, radiatedpower, threshold values and number of repetitions, simultaneously inorder to optimize the sensitivity of the sensors.

Therefore, the scope of the protection of the claims must not be limitedby the illustrations or by the preferred embodiments described by way ofexample, but rather the claims must comprise all the characteristics ofpatentable novelty that reside within the present invention, includingall the characteristics that would be treated as equivalent by theperson skilled in the art.

The disclosures in Italian Patent Application No. MO2004A000244 fromwhich this application claims priority are incorporated herein byreference.

1. An obstacle detection method, comprising the steps of: a) for eachsensor that belongs to an activation cycle, determining a power to beradiated, emitting corresponding ultrasound signals, and receiving echosignals reflected by at least one obstacle; b) depending on the echosignals received, determining distances of corresponding sensors fromthe obstacle and amplifying the received echo signals according tocorresponding distances; c) selecting threshold values with whichsignals amplified according to said distances determined by b) are to becompared; d) determining, at each sensor cycle, a number of times forwhich signals that exceed a respective selected threshold value arerepeated, and, if said number is higher than a preset value, generatinga warning signal; e) determining an order of priority of the sensorsaccording to the distances determined in step b); f) determining anactivation sequence of the sensors according to the order prioritydetermined in step e); g) adapting a sensing cycle of the sensorsaccording to an activation sequence determined in step f); wherein thesending cycle adapted in step g) excludes, for a preset number of cyclesthat is greater than zero, sensors that in step a) have not received anecho signal; and wherein said step e) of determining the order ofpriority comprises the steps of: - associating with each sensor a valueof the distance from the obstacle detected by the sensor; - determininga value that corresponds to a mininum detected distance and replacingsaid determined value with a value equal to a sum of said minimumdistance value and of a priority threshold value; and - assigning to thesensor that detected said minimum distance a priority status.
 2. Theobstacle detection method of claim 1, wherein said step e) fordetermining the order of priority further comprises the steps thatconsist in: - at each sensing cycle, determining whether at least one ofthe detected distances is shorter than the sum of the minimum distancevalue and the priority threshold value; and - assigning to the sensorthat detected said shorter distance a priority status in addition tosensors that already have a priority status.
 3. The obstacle detectionmethod of claim 2, wherein the sensing cycle adapted in step g) providesfor the more frequent activation of the sensors having a priority statuswith respect to the sensors that do not have a priority status.